K-S Relationship identification technique for use with EBSD

MC MARINELLI; MG MOSCATO; J SIGNORELLI; A EL BARTALI; I ALVAREZ

Brno

Conferencia; 6th International Cnference on Materials Structure & Micromechanics of Fracture; 2010

Institute of Physics of Metrials - Academy of Science of the Czech Republic

Duplex Stainless Steel (DSS) solidifies from the liquid phase to a completely ferritic structure (α). Austenite grains (γ) appear by solid phase transformation as cooling proceeds leading to an interconnected austenite-ferrite structure. Both phases are related by near Kurdjumov-Sachs (K-S) crystallographic relationships: {111}γ//{110}α [110]γ//[111]α. This efficiency of the coupling between phases is important for predicting the propagation of slip band from the austenite to the ferrite, which plays an important role in the crack formation process. These relations were experimentally studied using Transmission Electron Microscopy, but this technique allows only to study a small area of the specimen. In order to analyze the existence of the K-S relationship in flat specimens of hot- and cold-rolled UNS S32750 DSS plates, Electron Backscattered Diffraction (EBSD) technique was used to determine the local crystallographic properties of both phases. Furthermore, in order to relate the plastic deformation to the K-S relationship, the specimen was subjected to a low-cycle fatigue test at constant plastic strain amplitude of 1.5×10−3. About 14053 couples of α/γ grains were analized. However, crystallographic K-S relationships were rarely observed between α/γ phases and thus the flow of plasticity was nearly inhibited between them. In conclusion, microcracks were mostly nucleated at grain boundaries.